The RAFO Wikipedia page shows the air force ensign - light blue with the national flag in the canton and a roundel (white-edged red disk with white silhouette of the national emblem) in the lower fly.
Željko Heimer, 31 Mar 2012

Since 1959 , the royal air force of Oman (al-Quwwat al-Jawwiya al-Sultanat
Oman) has had five markings, according to
[Cochrane & Elliott (1998).
I must admit that I couldn't find all of them in photos, and I think that the
last two (which are really fin flashes) are used side by side with a third
fin flash which is the national flag.
According to
[Cochrane & Elliott (1998) the first roundel was like the Japanese (red disc with
white border) and the fin flash was a white shield charged with the national
emblem in red (a mirror of a later flash). Those markings were in use
between 1959-1965
In 1965 a new marking was adopted. The roundel was charged also with the
national emblem (as on Air Force Flag 1970-1995. The fin flash reversed its colors and
consisted of a red shield
and white emblem.
In 1970, a green border replaced the white, and wings were added to the emblem. The
fin flash was removed.
In 1977, the roundel was removed and the previous fin flash became the sole
marking.
In 1983, the color of the shield was changed to light blue.
All the above is based on
[Cochrane & Elliott (1998).
[Wheeler (1986) reported the blue shield and the
national flag both as fin flashes. He
also reported the some aircraft are using the old red shield.
Photos of the national flag being used as fin flash can be seen at
http://www.airliners.net/open.file/468818/L/ and
http://www.airliners.net/open.file/339253/L/.
A photo of the red shield can be found at
http://www.airliners.net/open.file/190425/L/ (photo
taken in 1961 when, according to
[Cochrane & Elliott (1998) it was a white shield....) and
http://www.rob.clubkawasaki.com/jas26.jpg (photo taken in 1972 when,
according to [Cochrane & Elliott (1998) this fin flash was not in use anymore....)http://www.scramble.nl/om.htm shows at
the top the red shield with two photos, one
with blue and one with red (Strikemaster served 1968-2000, Jaguar serving
since 1977)
Seems to be a complex story.Dov Gutterman, 21 June 2004

The Aircraft Fin Flash in Correction 3 is the same as in Album 2000 - it seems to be a very rudimentary yellow shape of the national emblem in a light blue shield. The RAFO Wikipedia page shows a much more elaborate design for the fin flash.
It also mentions a roundel (white-edged red disk with white silhouette of the national emblem).Source: Correction 3 to the Album des Pavillons 2000 [pay00]Željko Heimer, 31 Mar 2012